Autonomic Cardiovascular Dysregulation at Rest and During Stress in Chronically Low Blood Pressure

Abstract

Abstract. Chronic low blood pressure (hypotension) is accompanied by symptoms such as fatigue, reduced drive, faintness, dizziness, cold limbs, and concentration difficulties. The study explored the involvement of aberrances in autonomic cardiovascular control in the origin of this condition. In 40 hypotensive and 40 normotensive subjects, impedance cardiography, electrocardiography, and continuous blood pressure recordings were performed at rest and during stress induced by mental calculation. Parameters of cardiac sympathetic control (i.e., stroke volume, cardiac output, pre-ejection period, total peripheral resistance), parasympathetic control (i.e., heart rate variability), and baroreflex function (i.e., baroreflex sensitivity) were obtained. The hypotensive group exhibited markedly lower stroke volume, heart rate, and cardiac output, as well as higher pre-ejection period and baroreflex sensitivity than the control group. Hypotension was furthermore associated with a smaller blood pressure response during stress. No group differences arose in total peripheral resistance and heart rate variability. While reduced beta-adrenergic myocardial drive seems to constitute the principal feature of the autonomic impairment that characterizes chronic hypotension, baroreflex-related mechanisms may also contribute to this state. Insufficient organ perfusion due to reduced cardiac output and deficient cardiovascular adjustment to situational requirements may be involved in the manifestation of bodily and mental symptoms.

Cerebral blood flow modulations during antisaccade preparation in chronic hypotension

“…In contrast to sympathetic control, vagal activation and deactivation can produce heart rate fluctuations within this relatively fast time scale (Berntson, Quigley, Norman, & Lozano, ). Both the smaller heart rate deceleration in hypotensive participants and the restriction of the initial heart rate increase in the antisaccade condition compared to the normotensive group are in line with previous findings of reduced cardiovascular reactivity in chronic hypotension (Covassin, de Zambotti, Cellini, Sarlo, & Stegagno, ; Duschek et al, ; Duschek, Hoffmann, Montoro, & Reyes del Paso, ).…”

“…As initially stated, evidence of deficits in executive functions in hypotension is inconsistent. In contrast to previous studies (Duschek et al, 2005;Duschek, Hoffmann, Reyes del Paso, & Ettinger, 2017;Sarlo et al, 2013;Weisz et al, 2002), the inclusion of a prosaccade control condition in the present study allowed explicit differentiation between deficits in basic attentional and executive functions. The similar magnitude of the group difference in antisaccade and prosaccade conditions clearly challenges the assumption of selective executive dysfunctions in hypotension.…”

“…A limitation of the study pertains to the recruitment of the hypotensive sample according to WHO () criteria (i.e., systolic blood pressure below 100 mmHg in women and 110 mmHg in men), which are relatively lenient (cf. Covassin et al, , ; Duschek et al, ). Although these criteria are still widely accepted, more recently proposed definitions include lower systolic cutoff values and also take into account the diastolic value.…”

“…Autonomic dysregulation is substantially involved in the genesis of chronic hypotension, where reduced sympathetic tone appears to play a key role (Covassin, de Zambotti, Cellini, Sarlo, & Stegagno, ; Duschek, Dietel, Schandry, & Reyes del Paso, ). Various studies have demonstrated diminished sympathetic cardiac outflow in hypotension expressed as lower contractility and stroke volume and longer pre‐ejection period (Covassin, Zambotti, Cellini, Sarlo, & Stegagno, ; De Zambotti et al, ; Duschek et al, ; Duschek et al, ). In addition, diminished electrodermal activity (EDA) has been reported in hypotension, in terms of reduced tonic EDA and a lower rate of spontaneous EDA fluctuations (Fredrikson et al, ; Richter‐Heinrich, Borys, Sprung, & Läuter, ).…”

“…The study was part of a larger project on cardiovascular regulation and cerebral blood flow during executive functions in hypotension (Duschek, Hoffmann, & Reyes del Paso, ; Duschek, Hoffmann, Reyes del Paso, & Ettinger, ). The sample included 39 individuals (37 women, 2 men) with hypotension according to the WHO () definition and 40 control persons with normal blood pressure (37 women, 3 men).…”